This 17th-century sovereign was named after the 9th-century Emperor Seiwa[4] and go-(後?), translates literally as "later;" and thus, he could be called the "Later Emperor Mizunoo". The Japanese word go has also been translated to mean the "second one", and in some older sources, this emperor may be identified as "Mizunoo II".

Masahito-shinnō became emperor following the abdication of his emperor-father. The succession (the senso) was considered to have been received by the new monarch; and shortly thereafter, Emperor Go-Mizunoo is said to have acceded (the sokui).[11] The events during his lifetime shed some light on his reign. The years of Go-Mizunoo's reign correspond with a period in which Tokugawa Hidetada and Tokugawa Iemitsu were leaders at the pinnacle of the Tokugawa shogunate.

29 June 1596: The birth of an Imperial prince who will become known by the posthumous name of Go-Mizunoo.[12]

26 November 1614 (Keichō 19, 25th day of the 10th month): There was a strong earthquake. The same year a great bell for the Daibutsu Temple in Kyoto was cast.[6]

1615 (Keichō 20): Osaka Summer Battle begins

1615 (Genna 1): Tokugawa Ieyasu and his son, Shogun Hidetada, marched again to Osaka Castle, which was captured and burned; but Hideyori managed to flee to Satsuma where he had prepared a refuge in advance.[6]

6 January 1616 (Genna 2, 17th day of the 4th month): Ieyasu died at Suruga.[6]

25 September 1617 (Genna 3, 26th day of the 8th month): Former-Emperor Go-Yōzei died. He is buried at the North Fukakusa Burial Mound (深草北陵,Fukakusa no Kita no Misasagi?).

1620 (Genna 6): Tokugawa Masako, the daughter of Shogun Hidetada, entered the palace as a consort of the emperor; and the marriage was celebrated with great pomp.[15]

2 April 1620 (Genna 6, 30th day of the 2nd month): Severe fire in Kyoto.[6]

6 April 1620 (Genna 6, 4th day of the 3rd month): Severe fires in Kyoto.[6]

1623 (Genna 9): Tokugawa Iemitsu, son of Hidetada, came to the court of the emperor where he was created Shogun.[6]

1627 (Kan'ei 6): The "Purple Clothes Incident" (紫衣事件,shi-e jiken?): The Emperor was accused of having bestowed honorific purple garments to more than ten priests despite the shogun's edict which banned them for two years (probably in order to break the bond between the Emperor and religious circles). The shogunate intervened making the bestowing of the garments invalid. The priests which had been honored by the emperor were send into exile by the bakufu.[7]

22 December 1629 (Kan'ei 6, 8th day of the 11th month): Go-Mizunoo abdicated.[12] The emperor renounced the throne in favor of his daughter, Okiko, on the same day that the priests of the "Purple Clothes Incident" went into exile.[16] Okiko became the Empress Meishō.

Kugyō(公卿?) is a collective term for the very few most powerful men attached to the court of the Emperor of Japan in pre-Meiji eras. Even during those years in which the court's actual influence outside the palace walls was minimal, the hierarchic organization persisted.

In general, this elite group included only three to four men at a time. These were hereditary courtiers whose experience and background would have brought them to the pinnacle of a life's career. During Go-Mizunoo's reign, this apex of the Daijō-kan included: